Robert earned scores of 81, 93, 76, and 78 on four English tests. Determine his score on the fifth test if his average for the five tests was 85
Note that if his average was 85 he must have 85 * 5 = 425 total points
So his score on the fifth test was
425 - ( 81 + 93 + 76 + 78) = 97
(81+93+76+78 + x) / 5 = 85 solve for 'x'
Nice, both of you!